Boundary layer control system for aircraft



Jan. 24, 1961 R. w. JENSEN I 2,969,206

BOUNDARY LAYER GQNTROL SYSTEM FOR AIRCRAFT Filed DSC. 4. 1956 BOUNDARY LAYER CONTROL SYSTEM` FOR AIRCRAFT Raymond W. Jensen, Phoenix, Ariz., assignor to They Garrett Corporation, Los Angeles, Calif., a corporation of California Filed Dec; 4,1956, Ser. No'.626,1'41

4 Claims.r (Cl. 244-42) This invention relates to a boundary layer control-sys-4 tem` for aircraft, and more particularly to a boundary layer control system which is capable ofincreasing lift on airfoil surfaces of an aircraft-to assist lateral control thereof.

Boundary layer control systems are knowntwhich employl compressed air bled from the compressor of the aircraft' engine and the compressed airisvreleasedabove-thev wing iiaps or ailerons, thereby increasing liftI and per#v mitting the aircraft to assume ahigh angle of attack when landinglor taking'otf. In this mannerthe distances requiredfor takeoff and landing operations ofan aircraftV are greatly reduced. In addition, corresponding take= offl andrlandingspeeds are also reduced.

It has been a problem to maintain lateral stability of: anaircraft when landing .or taking od athighanglesfofat'- tack while employing boundary layer control air: to increase lift on the airfoil surfaces of the aircraft;

Accordingly, it is an object of. the-l present invention toprovide a boundary layer control system foraircraft. wherein lateral control airfoil elements. of4 an aircraft' actuate boundary layer control valveswhich automaticallyvary iiow ofl boundary layer control airlinaccordlanceV with varying, attitudes of theA airfoil elements;

Another object of the invention'is'toprovide a" bound; any; layer control'system wherein ailerons orliliaps actu; ate boundaryl layer control valves by means oflc'amsor other-'suitable mechanism,. thereby tending to modulate, the tiow1 ofn boundary layer` controlairI` over the@ airfoil elements infproportionto the degree ofr deflectioni'there ofrelative to the aircraft;

Another object-of the invention-'is to`provide`a'iboundlaryflayerl control systemlhaving. a1' dual pressure!rt-:gulator whiclipermitsafpredetermined` selection1of= adesiredp'res'.- sure.` to` be imposed uponf'pneumatic' actuatorsy of-valves located to control theliowfof boundary. layer-vcontroliair over the airfoil' elementsl of an: aircraft.'y

Another object ofy the .inventionfis to provider a' boundl ary, layler control system forzaircraft which permitsaipilotl to easilyl control level'flight' of theaircraft when landing. or taking oli'at y very.A h1gh=angles ofv attack.`

Further objects andI advantages of' the presenti inveni tionlmay'beapparentrfromithe followinglspeciiication, ap 4 pe'ndedclaimsandiaccompanying drawings in whichz Figure 1 is a fragmentary diagrammatic view.' o-f af boundary# layer control system' for aircraft;

Figure` 2- isi ai cross-sectional view of' an aircraft' wingshowingLtheA boundary layer control, air duct and aipilotvalve operated. by an aileron off the,I aircraft: wing; andff Figure 3f is=' a fragmentaryy sectionali viewI similar to' Figure butshowingther ail'e'ron. in` al different. operatingf'l positiom As shown in Figures 1 and 2 of the drawing, a conduit S-extends'- to the righthand' wingf: 1'12 ofi anaircraftl As shown! in Figurer 2 of the drawing, thefright-ha'ndiwingf 11; isv providedwith a-slot'12, which is arranged tofdirect:l hig'hpressure air over.- the I upper surfacefofganfaileron#13;;

atent O Patented. Jan. 24, 1961 ICC disposed for pivotal movement, relative to the wing, on=a-` pin 14.- As shown in Figure 3, a cam 15 is iixed to the== aileron 1-3= and when the aileron moves, the cam. actu ates. a plunger 16 of a pilot valve 17. This pilotvalve; isf arranged tocontrolV modulating action of a` main.- boundary layer control Valve 18 located to control flowf4 through the conduit 10, which will be hereinafter dei4 scribed indetail. A pilot valve 19,v similar` to theip'ilot'. valveY 17, isV arranged to control operation ofay second:A main boundary layer control valve 20. This valve 20:1 is disposed to control flow through the conduit 21;.- which issim'ilar to the conduitlll. The conduit 21I communicateswith a slot in the left-hand Wing; ofi the air.- craft similar to slot 12- infthe right wing; Inasmuch. as? the pilot valves 17 and 19 are identical, parts ofzth'e latter are identified by the same reference charactersem` ployed to designate corresponding parts oi" the'former.-

The plunger 16 of the pilot valve 17 is loaded in nor-- mally'open'position by'means of a spring 22, which :is supported ina casing 23, wherein the plunger 16 isrecip# rocally mounted. The plungerr 16 is provided` with a? tapered end portion 24, which is adapted to vary the". area' ofal passage 25 in the casing 23. The passage 25", communicates withV ambient pressure through openings` 23a in the casing.Y 23. The passage 25 also communi# cates, throughA a tube 26, with a chamberA 27; atone side` of. adiaphragm! 28 engaged by a springA 29' diss posed!tofoppose'movement of the diaphragm in responsei to pressureV in the chamber 27. A` stem` 30 is fixed? to" thediaphragm ZSand is' pivotally connected: byAv means"v of-alpin 311to afbellcrank' 32, Which'is linedtothesbub1 terfly valve- 18.-' Communicating with the conduit. 10t upstream of the'valve-18 isf a pressure supply tube'33;, which alsocommunicatesv with a solenoid valve :i4-having;y ay restricted orifice 36. A second restricted orifice 35.'v intercommuncateswith` then orifice 36 and the: chamber" A 27; Downstreamof` the valve 18 is a'tube 37'which'in-- tercommunica'tes with the conduit 10 an'dfa chamber 38t at the side of the diaphragm 28' opposite the,- chamber 27E,A

The solen'oidvalve 34is a normally closed-valve andiwhenl open permitsl liow through the orili'cef 36;. which; supplies iiow to the restricted orifice andi al similar,` restricted: orifice l 39; which communicates with a: chamber 40. Adjacentlto the chamber 40 is a'diaphra'gm 4f; connected by a` stem 42 to a bell crank` 43 which isi? xed to the butterfly valve 20. A spring 44lengages the.`- diaphragm 4T and4 tends tol oppose movement of the diaphragm 41v under: pressure in the chamber 4t).y Aw chamber 45 is.A arranged to contain pressurel which` acts; on` thev diaphragm 41* in opposition'to that inthefchambel? 40: A- tube 46' intercommunicatesv with the' chamber 45:-A and. the' conduit 21' downstream ofthe valve120..

AS1 tube 47 communicates with the solenoid=valve 34;.. oriices 35= aud-39; and` also-with a dual pressure: regu# lato'r 48. This regulator is arranged-for use inselectingf: either of two different pressures which may exist in the'.1 chambers 27 and 40. This pressure regulator is prof vided: with' a blowo-iff valve 49 comprisinga diaphragm 49afaud; a-stationary ball valve element 4%.YV Af springi Si); tends to maintain the valve 49 in normallyv closed:- position.- This spring; Sti resists the opening' ofl the; blowoffwvalve49 until a given-pressure existsinfthe tube:- 47V andactsfron thediaphragm-49a, whereuponthe blowe olf val-ve 49 permits escape of air from the tubeVv 47. Ai second4 blowoi.y valve, 51 is subjected` to the outlet pressurefofthe blowolvalve 49. The blowofi valve. 51-` isf.y similar in construction to that of the valve 49= andqiss` provided-witha spring 52,'having preloadedstressgrea'terrv than thatofithe` springt), whereby thezblowoff pres?1 o sure of the valveaSi-is: greater than that ofthe vali/e749.ry

The blowoi-valve 51; is,` also provided with a ventopenf ing 52a so that it may discharge to the surrounding atmosphere. Thus, the blowoff valves 49 and 51 in series may be utilized to maintain a high pressure in the tube 47 and chambers 27 and 4t). A vent valve 53 is disposed ot communicate with pressure intermediate the blowoif valves 49 and 51. This vent valve 53 is a normally open solenoid valve which permits pressure to escape at the outlet of the blowcff valve 49 when the solenoid valve is de-energized. Thus, the blowoif valve 49 may be operated by itself to maintain a low pressure in the chambers 27 and 40, and when the valve 53 is energized and moves to the closed position, it will cause the blowoff valves 49 and 51 to operate in series, whereupon said high pressure is maintained in the chambers 27 and 40.

- When the present boundary layer control system is operated in connection with an aircraft, the pilot valves 17 and 19 are actuated in proportion to the movement of the aircraft wing ailerons by means of cams 15, whereby the main boundary layer control valves 18 and 20 are caused to modulate ow of boundary layer control air to the slots 12 above the ailerons.

Referring to Figure 3 of the drawings, for example, it will be seen that downward movement of the aileron 13 causes the cam 15 to force the tapered portion 24 of the plunger 16 inwardly into the passage 25, which restricts the same. Pressure in the chamber 27 is thus increased, due to the fact that it is supplied with a constant volume of air through the restricted orifice 35 and by varying the leak olf through the passage 25, the pressure downstream of the orice 35 will vary. The plunger 16, when actuated by the aileron 13, is thus capable of modulating pressure in the chamber 27. Such modulation of the pressure in the chamber 27 causes corresponding deflection of the spring 29 and a relative opening movement of the valve 18. This valve 18, however, is a pressure regulating valve and when pressure downstream of the valve 18 exceeds a predetermined amount, pressure sensed in the chamber 38 acts against the diaphragm 28 to oppose pressure in the chamber 27. The valve 18 thus operates as a ow control valve, and therefore tends to increase boundary layer flow in direct proportion to downward deection of the aileron 13. Conversely, upward deflection of the aileron 13 causes a proportional decrease of ow of boundary layer control air through the slot 12.

- Operation of the pilot valve 19, in co-operative relation with the main boundary layer control valve 20, is similar to that of the pilot valve 17 and the main boundary layer control valve 18.

. It will be understood that when a wing of an aircraft tends to dip downwardly, the present boundary layer control system automatically assists action of the respective aileron to increase lift on the particular wing, in order to maintain level flight of the aircraft. As the pilot actuates the aircraft ailerons to maintain level flight of the aircraft, the system will allow the aileron that is lowered to auto-matically increase the boundary layer airflow over the lowered aileron thus increasing the lift on the particular wing. The opposite result will take place on the aileron that is raised thus decreasing the lift on the opposite wing. The combination of increased lift on one wing and decreased lift on the opposite wing will greatly assist the pilot in maintaining the aircraft in a level ight position. Thus the present boundary layer control system readily assists a pilot in maintaining level ight of an airplane when taking off or landing at high angles of attack. s

The dual pressure regulator 48 is controlled by the solenoid valve 53, which may be electrically connected to a switch in the pilots compartment. When the solenoid valve 53 is energized and in closed position, both the blowolf Valves 49 and 51 operate in series, maintaining a high pressure in the chambers 27 and 40, which tends to maintain a fully open position of the valves 18 and 20. Thus, the maximum ow of boundary layer control air through the slots 12 may be permitted, whereby an extremely high angle of attack of the aircraft may exist due to the increased lift which is created upon the airfoil surfaces. At this high angle of attack, the aircraft may be landed at low speed and on a very short runway.

Maximum boundary layer control air flow constitutes a very substantial portion of the aircraft engine compressor output, and therefore reduces thrust of the aircraft engine. In the event that an aircraft is landing at a high angle of attack, with maximum boundary layer control air flow, and at the same time is waved off the field, the remaining thrust of the aircraft engine may not be sufficient to take off with reasonable facility. The aircraft pilot may then de-energize the solenoid valve 53, whereby the blowoff valve 51 is bypassed, thus permitting the blowoff valve 49 to maintain a substantially lower pressure in the chambers 27 and 4t). This causes a partial closing action of the valves 18 and 20, which results in a reduction of boundary layer control air flow through the conduits 1t) and 21. Under these conditions the aircraft may maintain a reasonably high angle of attack; and since the flow of boundary layer control air is nominal, the aircraft engine has sucient thrust to take off with facility. It will therefore be apparent that the dual pressure regulator 48 provides a great operational advantage in connection with the boundary layer control system and that the boundary layer control valves 18 and 20, modulated by action of the aircraft ailerons, help maintain level flight of the aircraft when operating at high angles of attack.

It is desired to emphasize the fact that various modifications of the present invention may be resorted to in a manner limited only by the broad spirit and scope of the following claims.

I claim:

1. In a boundary layer control for aircraft the combination of: a movable airfoil element; an air flow system having a duct communicating with and extending in close proximity to said airfoil element for supplying boundary layer control air thereto; a main valve having a pneumatic actuator, said main valve being disposed in said system to control flow through said duct; pilot valve means in said system and communicating with said pneumatic actuator, said pilot valve being responsive to the movement of said airfoil element to control the operation of said actuator and main valve thereby varying the flow of air through said duct; regulator means in said system and communicating with the actuator for said main valve, said regulator means having a pair of pneumatic pressure regulators in series; and a bypass means for one of the pressure regulators, operation of said bypass means serving to select either of two different pressures to be supplied to said actuator.

2. In a boundary layer control system for aircraft, the combination of: a movable airfoil element; an air supply duct having an outlet disposed adjacent said airfoil element to supply boundary layer control air thereto; a main valve disposed for movement in said duct to vary the volume of air supplied to said airfoil element; actuating means for said main valve, said actuating means having a fluid pressure responsive member operatively connected with said main valve; means for conducting fluid from the inlet side of said main valve to one side of said pressure responsive member and from the outlet side of said main valve to the other side of such member; and a pilot valve communicating with said actuating means, said pilot valve being disposed to be actuated by said airfoil element to vary the fluid pressure applied to one side of the pressure responsive member of said actuating means.

3. In a boundary layer control system for aircraft, the combination of: a movable airfoil element; a duct having an outlet disposed adjacent said airfoil element to supply boundary layer control air thereto; a main valve disposed for movement in said duct to vary the volume of air supplied to said airfoil element; actuating means for said main valve, said actuating means having a fluid pressure responsive member operatively connected with said main valve; means for conducting fluid under pressure to said actuating means; pressure regulating means communicating with said fluid conducting means, said regulating means being adjustable to selectively vary the maximum pressures of fluid supplied to said actuating means; and a pilot valve communicating with said actuating means, said pilot valve being disposed to be actuated by said airfoil element to vary the fluid pressure applied to the pressure responsive member of said actuator in proportion to the extent of movement of said airfoil element.

4. In a boundary layer control system for aircraft, the combination of: a movable airfoil element; an air supply duct having an outlet disposed adjacent said airfoil element to supply boundary layer control air thereto; a main valve disposed for movement n said duct to vary the volume of air supplied to said airfoil element; actuating means for said main valve, said actuating means having a fluid pressure responsive member operatively connected with said main valve; means for conducting liuid from the inlet side of said main valve to one side of said pressure responsive member and from the outlet side of said main valve to the other side of such member; resilient means tending to move said pressure responsive member in a main valve closing direction; and a pilot valve communicating with said actuating means, said pilot valve being disposed to be actuated by said airfoil element to vary the fluid pressure applied to said pressure responsive member to move the same in a main valve opening direction.

References Cited in the le of this patent UNITED STATES PATENTS 1,512,597 Harmon Oct. 21, 1924 1,554,683 Mount et al. Sept. 22, 1925 2,162,940 De Florez June 20, 1939 2,478,793 Trey Aug. 9, 1949 2,700,516 Nazir Jan. 25, 1955 

